Urinary - Chapter 26 A&P ii

Stages of blood flow through kidney

Renal Artery - interlobar artery - arcuate artery - afferent artery (comes in) - glomerular capillaries - efferent artery (comes out) - peritubular capillaries (around pct/dct) - vasa recta (bottom part of LOH) peritubular capillary (bc it surrounds dct), arcuate vein - interlobar veins - renal vein - inferior vena cava - out to the heart

difference between the promixal / distal convulated tubule

Promixal - microvilli, absorption

Distal - no microvilli, secretion, shorter in length

How many times does the blood plasma get filtered through each day

65

Glomerular Filtration

Renal Process - Steps & Location

Filtration - Renal corpuscle - (pressure of blood affects how much is filtrated (non-selective)

Reabsorption - PCT - (amino acids are reabsorbed)

Secretion - DCT

filtration membrane

Too high GFR vs too low GFR

High - substances pass too fast & water/nutrients do NOT get reabsorbed

Low- substances pass too slow & waste products can get reabsorbed

How does fluid in the volume affect blood presssure

more fluid = higher pressure needed to circulate

What occurs in the nephron renal corpuscle

Filtration

What is filtrate composed of

Anything smaller than proteins, water/glucose/amino acid/albumin/electrolytes (NA+, K+, CA2+, HCO-,CI-3), urea, uric acid, creatinine

Purpose of the proximal convulated tube

reabsoprtion of filtrate

• everything but urea, uric acid, and creatinine can be reabsorbed

Function of Loop of Henele

Concentrate the urine

Distal convulated tubule

Collecting Duct

What occurs when the GFR is too high

substances pass quickly & does not get reabsorbed

What occurs when GFR is too low

Substances r filtrated too slowly & waste products can enter back into the body

GFR Mechanism - Myogenic

smooth muscle - afferent arteriole

high blood pressure - smooth muscle contracts in response to decrease in GFR

Low blood pressure - smooth muscle dilates to increase GFR (and blood flow)

GFR Mechanism - Tubuloglomerular feedback

detects NACI - is in the juxtaglomerular appartus (between afferent arteriole & DCT)

sends a message to dilate the afferent arrteriole to dialate (smooth muscle) when NACI is low in the LOH

hypertonic

blood cells crenate - more solutes less water

more concentrated urine

hypotonic

too much water, can pop like a balloon

more watery urine/”diluted”

Reabsorption in the loop of henle

Descending (1st)

• simple squamous, permeable to water back to our water

• solutes NA+ CI- & Urea move in, urine is super concentrated (hypertonic)

Ascending (2nd)

• simple cuboidal, impermeable to water, so it stays in LOH

• Solutes are removed (NACI, CI)

• pumps NaCl into interstitial fluid of the kidney (hypotonic)

Tubular Secretion

occurs in the DCT

• will secrete drugs/antibiotics

Urea

main waste product, highest concentration in urine

medullary concentration gradient

Interstitial fluid of the medulla has a higher concentration (hypertonic) compared to the cortex (hypotonic)

is dependent on countercurrent mechanism/urea cycling

antidiuretic hormone mechanism

ADH - triggered by low blood pressure/volume

produced by hypothalamic neurons & stores in the posterior pituitary

osmoreceptors in the hypothalamus detect high solute concentration, stimulating adh to be released when blood pressure drops, which increases h2o reabsorption from DCT/CD

results in increased water in the blood

Diabetes insipidus - insufficent adh secretion, can cause thirst & frequent urination d

Renin Angiotensin Aldosterone mechanism

same as ADH/ works with it, triggered by low blood pressure, but works on reabsorbing sodium from the DCT/CD, then the water follows it.

Angiotensinogen (liver) is turned into angiotensin I (lungs) by renin (in the JGC of the kidney)

Renin (enzyme) is released by juxtaglomerular cells within the kidney

Renin is then converted to angiotensin I (in the liver)

Angiotensin I is converted into angiotensin II by ACE in the lungs

Angiotensin II then releases aldosterone, with the help of the adrenal cortex (when stimulated) alderstone, then stimulates NA uptake

ANH Hormone

secreted by the right atrium of the heart, inhibits NA+ reabsorption in the DCT/CD, results in more water in urine, and inhibits ADH/aldosterone

triggered by high blood pressure

Steps to regulate blood pressure - in the case of high blood pressure

Blood volume is too high - baroreceptors send message to hypothalamus that causes

• posterior pituitary inhibits ADH

• JGA inhibits secretion of renin, decreases aldesterone

• heart muscle increases ANH

• SNS causes vasodilation to renal arteries = increase filtration

• ANH decreases NA reabsorption, more water & sodium in urine

StepsRegulation of blood pressure - too low

• posterior pituitary increases ADH secretion

• JGA releases renin

• cardiac muscles inhibit ANH

• SNS causes vasoconstriction of renal arteries = decrease filtration

Urine transportation/movement

ureters - urinary bladder (detrusor muscle, trnasitional epithelium & can hold 1L of urine) - trigone interior of urinary bladder

Urinary sphincters

Internal

• smooth muscle, involuntary

External

• voluntary, skeletal muscle

Male urethra is much longer, female urethra is shorter, creating more utis (in the bladder)

peristalsis

moves urine thru ureters from the renal pelvis to the urinary bladder until a certain amount, prevents backflow

Micturition reflex

activated when the bladder is stretched

• parasympathetic causes detrusor muscle to contract & internal sphincter relaxes, involuntary

• decreased somatic motor action cases external sphincter to relax

• urine flows from the bladder

• ability to inhibit micturition becomes voluntary around 2-3 years old

What is the main purpose of countercurrent mechanisms & the three types

Maintains the concentration gradient of the medulla pyramids (within the kidney)

Countercurrent Multiplier

• Occurs in the LOH

• Descending limb - water comes out into the interstitial fluid (by osmosis)

• Ascending limb - sodium comes out depending on bodily needs, which can greatly increase solute concentration (hypertonic)

Countercurrent Exchanger

• occurs in the vasa recta (capillaries surrounding the LOH)

• maintains the high solute concentration, “equal exchange”

Urea Cycling

• Urea is added to the interstitial fluid to raise the solute concentration, never returns into the body.

Urethritis & cystsis

Urethritis - inflammation of the urethra

Cystitis - inflamation of the urinary bladder

Pyelonphritis

Inflammation of kidneys - more grave

Glomerulonephritis

Inflammation of the filtration membrane within the renal corpuscle, plasma protein & blood cells enter the filtrate

Acute glomerulonephritis - bacteria-caused, can be resolved by itself within days.

chronic glomerulonephritis - dialysis/kidney transplant needed, due to infection, where filtration membrane is replaced with connective tissue

Diabetes inspidus vs Diabetes mellitus

Inspidus - no ANH

Mellitus - excess glucose levels ddamage blood vessels in kindey/nephron